more work on porting rc command parsing to Go

tools/cmd/at/set_spacing.go

@@ -0,0 +1,53 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package at
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"kitty/tools/utils"
+)
+
+func parse_set_spacing(args []string) (map[string]interface{}, error) {
+	ans := make(map[string]interface{}, len(args))
+	mapper := make(map[string][]string, 32)
+	types := [2]string{"margin", "padding"}
+	for _, q := range types {
+		mapper[q] = []string{q + "-left", q + "-top", q + "-right", q + "-bottom"}
+		mapper[q+"-h"] = []string{q + "-left", q + "-right"}
+		mapper[q+"-v"] = []string{q + "-top", q + "-bottom"}
+		mapper[q+"-left"] = []string{q + "left"}
+		mapper[q+"-right"] = []string{q + "right"}
+		mapper[q+"-top"] = []string{q + "top"}
+		mapper[q+"-bottom"] = []string{q + "bottom"}
+	}
+	for _, arg := range args {
+		k, v, found := utils.Cut(arg, "=")
+		if !found {
+			return nil, fmt.Errorf("%s is not a valid setting", arg)
+		}
+		k = strings.ToLower(k)
+		v = strings.ToLower(v)
+		which, found := mapper[k]
+		if !found {
+			return nil, fmt.Errorf("%s is not a valid edge specification", k)
+		}
+		if v == "default" {
+			for _, q := range which {
+				ans[q] = nil
+			}
+		} else {
+			val, err := strconv.ParseFloat(v, 64)
+			if err != nil {
+				return nil, fmt.Errorf("%s is not a number", v)
+			}
+			for _, q := range which {
+				ans[q] = val
+			}
+		}
+
+	}
+	return ans, nil
+}